This invention relates to an improved process for production of ortho-nitrobenzonitriles. Compounds of this type have the general formula ##STR1## in which R.sub.1 and R.sub.2 independently represent hydrogen or various electron-withdrawing groups such as nitro, cyano, halomethyl (particularly trihalomethyl), lower alkylsulfonyl, and halo-(lower alkyl)sulfonyl.
Various processes are known for the production of compounds of this type including the general process of cyanation of a similarly substituted halobenzene.
One such process is described in U.S. Pat. No. 2,195,076. That process uses a combination of cuprous cyanide and a compound capable of forming a "double compound" with the cuprous cynaide, particularly certain nitrogenous bases. The patent states that in many cases it is preferable to add inorganic salts, preferably copper salts, or also halides of alkali metals, aluminum, zinc, mercury or iron. This patent contains a total of 33 examples describing production of various compounds by the general process. One of the compounds prepared, in Example 18, is 4-cyano-3-nitro-1-trifluoromethylbenzene. In that example the compound is produced using a combination of cuprous cyanide, cuprous chloride and quinoline. An attempt was made to repeat this example to determine the yield of the product, as the example did not provide such information. However, little or no desired product was observed, with tarry products predominating. Lowering of the temperature did not result in any significant improvement.
Most of the examples of U.S. Pat. No. 2,195,076 show the use of cuprous cyanide alone or in combination with another copper salt, usually cuprous chloride or bromide. The only salt of any other metal which is disclosed in an example used in combination with cuprous cyanide, is sodium cyanide.
Japanese Patent Application 60/47830 (publication number) of Nippon Kayaku Company discloses a method for producing ortho-nitrobenzonitrile compounds employing an alkali metal cyanide, cuprous chloride (or cuprous chloride plus a cupric salt) and a polar aprotic or basic solvent.